$end
$molecule
0 1
Chapter 10: Molecular Properties and Analysis
575
H
0.
0.
0.0
H
0.
0.
1.5000
$end
$rem
JOBTYPE
SP
SCF_GUESS
CORE
METHOD B3LYP
BASIS
G3LARGE
purcar 222
THRESH
14
MAX_SCF_CYCLES
80
PRINT_INPUT
TRUE
SCF_FINAL_PRINT
1
INCDFT
FALSE
XC_GRID 000128000302
SYM_IGNORE
TRUE
SYMMETRY
FALSE
SCF_CONVERGENCE
9
$end
@@@
$comment
Now one RIB05 extraiteration after B3LYP
to generate the oddelectron atomic population and the
correlated bond order.
$end
$molecule
READ
$end
$rem
JOBTYPE
SP
SCF_GUESS
READ
EXCHANGE BM05
purcar 22222
BASIS G3LARGE
AUX_BASIS riB05ccpvtz
THRESH
14
PRINT_INPUT
TRUE
INCDFT
FALSE
XC_GRID 000128000302
SYM_IGNORE
TRUE
SYMMETRY
FALSE
MAX_SCF_CYCLES
0
SCF_CONVERGENCE
9
dft_cutoffs 0
1415 1
$end
@@@
$comment
Finally, a fully SCF run RIB05 using the previous output as a guess.
The following input lines are obligatory here:
purcar 22222
Chapter 10: Molecular Properties and Analysis
576
AUX_BASIS riB05ccpvtz
dft_cutoffs 0
1415 1
$end
$molecule
READ
$end
$rem
JOBTYPE
SP
SCF_GUESS
READ
EXCHANGE BM05
purcar 22222
BASIS G3LARGE
AUX_BASIS riB05ccpvtz
THRESH
14
PRINT_INPUT
TRUE
INCDFT
FALSE
IPRINT
3
XC_GRID 000128000302
SYM_IGNORE
TRUE
SCF_FINAL_PRINT
1
SYMMETRY
FALSE
MAX_SCF_CYCLES
80
SCF_CONVERGENCE
8
dft_cutoffs 0
1415 1
$end
Once the atomic population of odd electrons is obtained, a calculation of the corresponding correlated
bond order of Mayer’s type follows in the code, using certain exact relationships between
F
r
A
,
F
r
B
, and
the correlated bond order of Mayer type
B
AB
. Both new properties are printed at the end of the output,
right after the multipoles section. It is useful to compare the correlated bond order with Mayer’s SCF bond
order. To print the latter, use
SCF_FINAL_PRINT
= 1.
10.20
Quantum Transport Properties via the Landauer Approxima
tion
Quantum transport at the molecule level involves bridging two electrodes with a molecule or molecular sys
tem, and calculating the properties of the resulting molecular electronic device, including currentvoltage
curves, the effect of the electrodes on the molecular states, etc. For a general introduction to the field, the
following references are useful [143, 144].
The quantum transport code in QC
HEM
is developed by Prof. Barry Dunietz (Kent State) and his group.
This package is invoked by the
$rem
variable
TRANS_ENABLE
.
Chapter 10: Molecular Properties and Analysis
577
TRANS_ENABLE
Decide whether or not to enable the molecular transport code.
TYPE:
INTEGER
DEFAULT:
0
Do not perform transport calculations.
OPTIONS:
1
Perform transport calculations in the Landauer approximation.

1
Print matrices for subsequent calls for
tranchem.exe
as a standalone postprocessing
utility, or for generating bulk model files.
RECOMMENDATION:
Use as required.
Output is provided in the QC
HEM
output file and in the following additional files:
•
transmission.txt
(transmission function in the requested energy window)
•
TDOS.txt
•
current.txt
(IV plot if set)
•
FAmat.dat
(Hamiltonian matrix for follow up calculations and analysis)
•
Smat.dat
(Hamiltonian matrix for follow up calculations and analysis)
TChem requires two parameter files:
•
Transmodel.para
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 Fall '08
 Staff
 Quantum Chemistry, The Land, Computational chemistry, density functional theory, Job control, TDDFT, QC HEM